Cleanly stop the DMA engine even when no file is found. Following the bug report by Github user CRC-Mismatch

README.md

@@ -142,7 +142,7 @@ CPU usage increases dramatically when adding audio because the program has to up
 
 The RDS data generator lies in the `rds.c` file.
 
-The RDS data generator generates cyclically four 0A groups (for transmitting PS), and one 2A group (for transmitting RT). `get_rds_group` generates one group, and uses `crc` for computing the CRC.
+The RDS data generator generates cyclically four 0A groups (for transmitting PS), and one 2A group (for transmitting RT). In addition, every minute, it inserts a 4A group (for transmitting CT, clock time). `get_rds_group` generates one group, and uses `crc` for computing the CRC.
 
 To get samples of RDS data, call `get_rds_samples`. It calls `get_rds_group`, differentially encodes the signal and generates a shaped biphase symbol. Successive biphase symbols overlap: the samples are added so that the result is equivalent to applying the shaping filter (a [root-raised-cosine (RRC) filter ](http://en.wikipedia.org/wiki/Root-raised-cosine_filter) specified in the RDS standard) to a sequence of Manchester-encoded pulses.
 
@@ -164,6 +164,9 @@ The samples are played by `pi_fm_rds.c` that is adapted from Richard Hirst's [Pi
 
 ## History
 
+* 2014-10-19: bugfix (cleanly stop the DMA engine when the specified file does not exist, or it's not possible to read from stdin)
+* 2014-08-04: bugfix (ppm now uses floats)
+* 2014-06-22: generate CT (clock time) signals, bugfixes
 * 2014-05-04: possibility to change PS and RT at run-time
 * 2014-04-28: support piping audio file data to Pi-FM-RDS' standard input
 * 2014-04-14: new release that supports any sample rate for the audio input, and that can generate a proper FM-Stereo signal if a stereophonic input file is provided

src/pi_fm_rds.c

@@ -198,7 +198,7 @@ udelay(int us)
 }
 
 static void
-terminate(int dummy)
+terminate(int num)
 {
     if (dma_reg) {
         dma_reg[DMA_CS] = BCM2708_DMA_RESET;
@@ -208,7 +208,9 @@ terminate(int dummy)
     fm_mpx_close();
     close_control_pipe();
     
-    exit(1);
+    printf("Terminating: cleanly deactivated the DMA engine.\n");
+    
+    exit(num);
 }
 
 static void
@@ -419,7 +421,7 @@ int tx(uint32_t carrier_freq, char *audio_file, uint16_t pi, char *ps, char *rt,
     int data_index = 0;
 
     // Initialize the baseband generator
-    if(fm_mpx_open(audio_file, DATA_SIZE) < 0) return -1;
+    if(fm_mpx_open(audio_file, DATA_SIZE) < 0) return 1;
     
     // Initialize the RDS modulator
     char myps[9] = {0};
@@ -507,8 +509,6 @@ int tx(uint32_t carrier_freq, char *audio_file, uint16_t pi, char *ps, char *rt,
         last_cb = (uint32_t)virtbase + last_sample * sizeof(dma_cb_t) * 2;
     }
 
-    terminate(0);
-
     return 0;
 }
 
@@ -560,5 +560,7 @@ int main(int argc, char **argv) {
         }
     }
     
-    tx(carrier_freq, audio_file, pi, ps, rt, ppm, control_pipe);
+    int errcode = tx(carrier_freq, audio_file, pi, ps, rt, ppm, control_pipe);
+    
+    terminate(errcode);
 }